7005 vs 6061 aluminum (a nerdy, technical question)

Discussion in 'Cycling Equipment' started by Mike Miles, Jun 28, 2003.

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  1. Mike Miles

    Mike Miles Guest

    Alright, so this is a question for my mechanical engineer brethren, or you material scientists, or
    anyone else who deals with metals and metal alloys.

    I've found an article here <http://www.key-to-metals.com/ViewArticle.asp?ID=23> that states: <snip>

    system develop the highest room-temperature tensile properties of any aluminum alloys produced from
    conventionally cast ingots. <snip>

    Why, then, is a bike like the GF Tassajara (which I am going to buy), made from 7005 aluminum, is
    less expensive than the same frame in 6061 T6 aluminum (the GF Hoo Koo E Koo). I know the components
    play a difference, but that shouldn't account for an almost $200 price change. What gives?

    -Mike
     
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  2. Suzy Jackson

    Suzy Jackson Guest

    "Mike Miles" <[email protected]> wrote in message news:[email protected][192.168.1.55]...
    > Alright, so this is a question for my mechanical engineer brethren, or you material scientists, or
    > anyone else who deals with metals and metal
    alloys.
    >
    > I've found an article here <http://www.key-to-metals.com/ViewArticle.asp?ID=23> that
    > states: <snip>

    > system develop the highest room-temperature tensile properties of any aluminum alloys produced
    > from conventionally cast ingots. <snip>
    >
    > Why, then, is a bike like the GF Tassajara (which I am going to buy), made from 7005
    > aluminum, is less expensive than the same frame in 6061 T6 aluminum (the GF Hoo Koo E Koo). I
    > know the components play a difference, but that shouldn't account for an almost $200 price
    > change. What gives?

    The answer to your question lies in the "room temperature" bit. The T6 in the designator for the
    more expensive frame means that it's been heat treated to improve its tensile properties. This is
    done in a great big huge oven, and takes a long time (like a couple of days) to do properly, and
    results in a frame that's much stronger with no heat affected zones (from welding) than frames that
    haven't been heat treated.

    7005 ages (to some extent) at room temperature, which simply means that the brittle bits from
    welding become less brittle after a few weeks.

    Regards,

    Suzy
     
  3. Mike Miles

    Mike Miles Guest

    --On Sunday, June 29, 2003 6:11 AM +0000 Suzy Jackson <[email protected]> wrote:

    >
    > "Mike Miles" <[email protected]> wrote in message
    > news:[email protected][192.168.1.55]...
    >> Alright, so this is a question for my mechanical engineer brethren, or you material scientists,
    >> or anyone else who deals with metals and metal
    > alloys.
    >>
    >> I've found an article here <http://www.key-to-metals.com/ViewArticle.asp?ID=23> that
    >> states: <snip>

    >> Al-Zn-Mg-Cu system develop the highest room-temperature tensile properties of any aluminum alloys
    >> produced from conventionally cast ingots. <snip>
    >>
    >> Why, then, is a bike like the GF Tassajara (which I am going to buy), made from 7005
    >> aluminum, is less expensive than the same frame in 6061 T6 aluminum (the GF Hoo Koo E Koo). I
    >> know the components play a difference, but that shouldn't account for an almost $200 price
    >> change. What gives?
    >
    > The answer to your question lies in the "room temperature" bit. The T6 in the designator for the
    > more expensive frame means that it's been heat treated to improve its tensile properties. This is
    > done in a great big huge oven, and takes a long time (like a couple of days) to do properly, and
    > results in a frame that's much stronger with no heat affected zones (from welding) than frames
    > that haven't been heat treated.
    >
    > 7005 ages (to some extent) at room temperature, which simply means that the brittle bits from
    > welding become less brittle after a few weeks.
    >
    > Regards,
    >
    > Suzy
    >
    >

    Thanks for bringing up something I forgot to mention. From my reading, though, the article used
    tempered 6061 aluminum in its comparisons. I'm simply wondering if more is charged because they can
    advertise it as "aircraft-grade" aluminum, or if there really are advantages it has under bike
    conditions (6061 T6 performs very well at aircraft temperatures, hence its use).

    -Mike
     
  4. A Muzi

    A Muzi Guest

    "Mike Miles" <[email protected]> wrote in message news:[email protected][192.168.1.55]...
    > Alright, so this is a question for my mechanical engineer brethren, or you material scientists, or
    > anyone else who deals with metals and metal
    alloys.
    >
    > I've found an article here <http://www.key-to-metals.com/ViewArticle.asp?ID=23> that
    > states: <snip>

    > system develop the highest room-temperature tensile properties of any aluminum alloys produced
    > from conventionally cast ingots. <snip>
    >
    > Why, then, is a bike like the GF Tassajara (which I am going to buy), made from 7005
    > aluminum, is less expensive than the same frame in 6061 T6 aluminum (the GF Hoo Koo E Koo). I
    > know the components play a difference, but that shouldn't account for an almost $200 price
    > change. What gives?

    You haven't isolated your variables.

    Tube mills offer a wide range of prices within a given material based on cleanlines of the material
    ( control of impurities), method of tube fabrication ( wrapping and welding vs. cold drawing) finish
    quality of the tube both in terms of surface irregularities and dimensional control and final temper
    as delievered with any annealing or tempering procsses. Once past that, brand-name material sells
    for more money that the same tube without the label. Then the frame manufacturer gets involved with
    joining methods, quality control or lack thereof, finish method and time spent in finish. Finally,
    there's a big difference in volume on any given piece ( high volume can lower costs as fixtures and
    equipment can be dedicated for more efficiency and them amortized over more units.).

    Do we even know that the two frames are made in the same place?

    So the material specifcation is only one factor among many in the price of a final product.

    --
    Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
     
  5. Mike Miles

    Mike Miles Guest

    --On Sunday, June 29, 2003 10:06 AM -0500 A Muzi <[email protected]> wrote:

    > "Mike Miles" <[email protected]> wrote in message
    > news:[email protected][192.168.1.55]...
    >> Alright, so this is a question for my mechanical engineer brethren, or you material scientists,
    >> or anyone else who deals with metals and metal
    > alloys.
    >>
    >> I've found an article here <http://www.key-to-metals.com/ViewArticle.asp?ID=23> that
    >> states: <snip>

    >> Al-Zn-Mg-Cu system develop the highest room-temperature tensile properties of any aluminum alloys
    >> produced from conventionally cast ingots. <snip>
    >>
    >> Why, then, is a bike like the GF Tassajara (which I am going to buy), made from 7005
    >> aluminum, is less expensive than the same frame in 6061 T6 aluminum (the GF Hoo Koo E Koo). I
    >> know the components play a difference, but that shouldn't account for an almost $200 price
    >> change. What gives?
    >
    > You haven't isolated your variables.
    >
    > Tube mills offer a wide range of prices within a given material based on cleanlines of the
    > material ( control of impurities), method of tube fabrication ( wrapping and welding vs. cold
    > drawing) finish quality of the tube both in terms of surface irregularities and dimensional
    > control and final temper as delievered with any annealing or tempering procsses. Once past that,
    > brand-name material sells for more money that the same tube without the label. Then the frame
    > manufacturer gets involved with joining methods, quality control or lack thereof, finish method
    > and time spent in finish. Finally, there's a big difference in volume on any given piece ( high
    > volume can lower costs as fixtures and equipment can be dedicated for more efficiency and them
    > amortized over more units.).
    >
    > Do we even know that the two frames are made in the same place?
    >
    > So the material specifcation is only one factor among many in the price of a final product.
    >
    > --
    > Andrew Muzi www.yellowjersey.org Open every day since 1 April, 1971
    >
    >

    Good Point. I checked, and as best I can tell, the 7005's are made both in WI (with the 6061 T6
    frames) and in Taiwan. So I guess quality is an issue. This answers my specific question.

    All things being equal, though, if there were two frames made in the same facility, from the same
    quality of tubing, by the same method, which do you think would be the better bike? If I was at
    school, I might consider running the frame geometry through ADAMS/ANSYS with the two different
    materials and finding out. But since I'm at home, no dice.

    -Mike
     
  6. DiabloScott

    DiabloScott New Member

    Joined:
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    Fact 1: A 6061 tubeset will be cheaper than a 7005 tubeset from the same manufacturer.

    Fact 2: A 6061 tubeset is more adversely affected by the heat of welding than a 7005 tubeset.

    Fact 3: A 6061 FRAME maker reduces the weakening effects of welding with a relatively expensive heat treatment process (and perhaps a better welding protocol), whereas a 7005 frame maker uses a more expensive tubeset to minimize the effects of welding with a less expensive heat treatment.

    Opinion: Whether a particular 6061 frame is stronger (more resistant to crack propogation and therefore worth more) than an equivalent 7005 frame depends a LOT on the skill and expertise of the builder.

    DiabloScott, BSME
     
  7. Maurizio

    Maurizio Guest

    "DiabloScott" <[email protected]> ha scritto nel messaggio
    news:[email protected]...

    > Fact 3: A 6061 FRAME maker reduces the weakening effects of welding with a relatively expensive
    > heat treatment process (and perhaps a better welding protocol), whereas a 7005 frame maker uses a
    > more expensive tubeset to minimize the effects of welding with a less expensive heat treatment.

    That's exactly what Gary Fisher claims on his 2001 catalog. A Silver Series frame was made of an
    even more expensive tubeset than Gold and Platinum one, but the former is cheaper because it doesn't
    undergo an expensive heat treatment process.

    Ciao Maurizio, Bologna, Italy
     
  8. > Why, then, is a bike like the GF Tassajara (which I am going to buy), made from 7005
    > aluminum, is less expensive than the same frame in 6061 T6 aluminum (the GF Hoo Koo E Koo). I
    > know the components play a difference, but that shouldn't account for an almost $200 price
    > change. What gives?

    If you use 7005 tubes with fairly thick walls (heavy), you can pretty much skip the
    heat-treating process.

    6061, however, cannot safely be used in a welded frame without fairly extensive heat treating to
    bring it up to a reasonable strength. The cost of this heat treatment greatly exceeds the
    material cost of the tubes, and shoots the cost of a frame built from it well past that of a
    heavy 7005 frame.

    You can also use 7005 to build a very light frame, but then you're back into fancy heat-treating
    protocols.

    So basically you can use 7005 to build very inexpensive frames or fairly high-end, but the incentive
    over 6061 is primarily at the lower end (to reduce costs). At the upper end, 6061 is an extremely
    versatile material that still competes quite nicely with various exotic tubesets, as well as holding
    court over the vast middle ground.

    Fabrication costs are really the key ingredient here.

    --Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

    "Mike Miles" <[email protected]> wrote in message news:[email protected][192.168.1.55]...
    > Alright, so this is a question for my mechanical engineer brethren, or you material scientists, or
    > anyone else who deals with metals and metal
    alloys.
    >
    > I've found an article here <http://www.key-to-metals.com/ViewArticle.asp?ID=23> that
    > states: <snip>

    > system develop the highest room-temperature tensile properties of any aluminum alloys produced
    > from conventionally cast ingots. <snip>
    >
    > Why, then, is a bike like the GF Tassajara (which I am going to buy), made from 7005
    > aluminum, is less expensive than the same frame in 6061 T6 aluminum (the GF Hoo Koo E Koo). I
    > know the components play a difference, but that shouldn't account for an almost $200 price
    > change. What gives?
    >
    > -Mike
     
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